U.S. patent number 4,640,989 [Application Number 06/633,538] was granted by the patent office on 1987-02-03 for communications unit for executive work station.
This patent grant is currently assigned to Asher Technologies, Inc.. Invention is credited to Wilbur L. Riner, Bruce W. Watson.
United States Patent |
4,640,989 |
Riner , et al. |
February 3, 1987 |
Communications unit for executive work station
Abstract
A communications unit for an executive workstation which
provides a switching arrangement for interconnecting voice and data
lines with a computer and a telephone instrument. The
communications unit contains a microcomputer with memory which
provides connection patterns and number directory for quick access
to individuals and data services required by the user. In the
preferred embodiment, the communications unit is configured as a
printed circuit board that may be plugged into a desktop computer
for direct access to the computer's keyboard and CRT monitor so
that the user may use the keyboard and the monitor for all
communications. The communications unit also is capable of
connecting to a keysystem.
Inventors: |
Riner; Wilbur L. (Roswell,
GA), Watson; Bruce W. (Norcross, GA) |
Assignee: |
Asher Technologies, Inc.
(Roswell, GA)
|
Family
ID: |
24540033 |
Appl.
No.: |
06/633,538 |
Filed: |
July 23, 1984 |
Current U.S.
Class: |
379/93.14;
375/223; 379/110.01; 379/361; 379/386 |
Current CPC
Class: |
H04M
11/06 (20130101); H04Q 3/627 (20130101); H04Q
3/54533 (20130101) |
Current International
Class: |
H04Q
3/545 (20060101); H04Q 3/62 (20060101); H04M
11/06 (20060101); H04M 011/00 () |
Field of
Search: |
;179/2C,2DP,9BD,9BB
;375/5,8 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
MFJ Enterprises, Inc., advertisement for VIC-20/C-64 Modem, Run,
Mar. 1984, p. 35. .
Richvale Telecommunications, advertisement, "Developing a Mind for
the Future", Compute's Gazette, May 1984, p. 45. .
Eriksson et al, "Voice and Data Workstations and Services in the
ISDN", Ericsson Review, vol. 61, No. ISDN, May 1984, pp. 14-19.
.
BIZCOMP, Advertisement "There's Only One PC/XT Modem Designed to
Let Both You and Your Computer Talk,"..
|
Primary Examiner: George; Keith E.
Attorney, Agent or Firm: Oltman and Flynn
Claims
I claim:
1. A communications unit comprising a work station having a desktop
computer, the desktop computer having an access opening for a
printed circuit board, a keyboard and a monitor screen, the
communications unit further including, mounted on said circuit
board:
a microcomputer;
a switch matrix;
a first plurality of horizontal lines included in the matrix; at
least two external lines accessable by the horizontal lines;
a second plurality of vertical lines accessable by the horizontal
lines;
a plurality of line monitors equal to said first plurality, each
line monitor being operatively responsive to a respective
horizontal line and each consisting of an analog-to-digital
converter connected to the monitored line to sense the voltage on
that line and convert that voltage to a digital signal, said
converter operatively engaging an AND-gate addressable by said
micro-computer to provide a digital indication of any status of the
respective horizontal line in response to addressing by said
microcomputer;
a third plurality of selectively switchable crosspoints for
selectively associating any horizontal line with any vertical line,
said crosspoints selectively controllable by
a crosspoint control circuit;
said microcomputer controlling said crosspoint control circuit;
a data modem responsively connected with a first one of said
vertical lines for receiving and sending of data;
a telephone network responsively connected with another one of said
vertical lines, said telephone network connected with a telephone
handset having a receiver and a transmitter for voice transmission;
and
means for connecting said communications unit with a desktop
computer.
2. Communications unit as recited in claim 1, wherein said
microcomputer comprises:
a central processing unit for executing instructions in a control
program;
a read-only memory for storing control programs for controlling
said communications unit;
a random access memory for storing transient data;
an interface circuit for operatively interfacing between said
microcomputer and said modem, said telephone network, and said
desktop computer.
3. A communications unit as recited in claim 2, wherein said
horizontal lines and said vertical lines each comprise a tip and a
ring conductor for voice transmission.
4. A communications unit as recited in claim 3 further
comprising:
a line control circuit associated with a third one of said vertical
lines, said line control circuit being connectable to anyone of the
horizontal lines;
means included in the line control circuit being responsive to said
microcomputer for closing the connection between said tip and ring
lead of the third vertical line for seizing and for pulsing said
third vertical line;
a tone receiving circuit operatively associated with said third
vertical line for receiving call progress tones and operatively
associated with said microcomputer for transmitting call progress
indications to said microcomputer.
5. Communications unit as recited in claim 4 further comprising a
tone sender included in said line control circuit, said sender
operatively responsive to said microcomputer for sending network
control tones.
6. A communications unit as recited in claim 1 wherein at least one
of said horizontal lines is connected with a keytelephone system
having an A-lead and a lamp lead, said communications unit further
comprising:
means for engaging said A-lead associated with the keytelephone
system for transmitting a hold condition to said line of the
keytelephone system; and
means for engaging said lamp lead associated with the keytelephone
system for signalling line status from said keytelephone system to
said line monitor circuit.
7. A communications circuit as recited in claim 1 wherein said
access opening comprises:
a circuit board connector associated with the backplane wiring of
said desktop computer:
a card edge connector on said printed circuit board for inserting
said board into said circuit board connector for associating said
communications unit with the backplane wiring of the computer.
8. A communications unit as recited in claim 1 wherein each of said
crosspoints comprises:
a crosspoint relay having:
a latching circuit operatively responsive to said crosspoint
control circuit for operating the crosspoint relay;
at least two make contacts for connection to said horizontal
lines.
9. A communications unit as recited in claim 8 and further
comprising:
an address decoder operatively responsive to the microcomputer
interface circuit for producing address signals for said
crosspoints:
set and reset AND-gates responsive to the microcomputer for setting
and resetting the latching circuits.
Description
BACKGROUND
The invention relates to communication units for use with small
computers, and more particularly for use with a desk top computer
of the now widely used type having a data base suitable for
administrative or business type applications.
Small computers of the desktop type are increasingly finding use as
so-called executive work stations. In this type of application
several different modes of operation for a small computer may be
invoked by the user depending upon his particular needs.
In one such mode, the desktop computer may be used to present
different data families organized in a form that has the greatest
degree of utility for the user. Typical of such type of data
families is inventory data, personnel data, financial data and so
forth.
In another mode of operation, such desktop computers may be coupled
to voice and data communication lines with suitable switching
arrangements for the purpose of setting-up voice and data
connections to other individuals and for setting-up conferences
with groups of individuals.
In still another mode of operation the desktop computer may be
provided with suitable data-switching arrangements for connecting
with data bases or message storage memory bases for retrieval and
deposit of messages.
In the hereinabove described modes of use it has been found that a
relatively small computer provided with suitable programming and
connected via suitable switching arrangements for voice and data
lines can be programmed to dial-up almost any desired patterns of
connections that may be stored in the computer's user-accessible
memory. Furthermore, the computer can be programmed in advance to
overcome almost any types of problems normally encountered in the
setting up of such communications patterns, such as busy or
unavailability conditions and the like.
SUMMARY AND PRIOR ART
Inventors have in recent years sought to combine the versatility of
the desktop computer with switching and communications facilities
for providing an executive work facility ("work station").
U.S. Pat. No. 3,887,062 discloses a digital computer having
terminals such as teleprinter, keyboard and acoustic couplers for
connection with telephone lines.
U.S. Pat. No. 4,0151,326 discloses an arrangement for switching-on
and initialization of a data terminal.
U.S. Pat. No. 4,201,887 discloses a data communications terminal
that provides a handheld automatic tone-dialling arrangement,
comprising a microprocessor with a memory and a keyboard.
U.S. Pat. No. 4,253,157 discloses a data access system for
providing data bank access to a subscriber terminal via telephone
lines.
U.S. Pat. No. 4,367,374 discloses a modem telephone interface
circuit for interfacing between a telephone line and a telephone
instrument and a data terminal.
U.S. Pat. No. 4,403,111 discloses apparatus for interconnecting
data communications equipment and data terminal equipment.
The communications circuit of the present invention provides a
communications unit for interfacing between voice and data lines
that is highly adapted for close association, electrically and
physically, with a desktop type computer, and which provides the
means for connection with such lines and for controlling them in
accordance with the particular type line control protocol required
for the lines. The communications unit further provides access to a
conventional telephone instrument for voice and tone communication
with the voice lines.
In the preferred embodiment of the invention, the communications
unit is also adapted for communication with internal switching
systems such as PABX systems and Keytelephone systems. Such
switching systems usually have a line control protocol which is
different from that required for control of central office
telephone lines.
In the preferred embodiment the communications unit is closely
associated, physically, with a desktop computer in that it is
assembled and wired on a circuit board of such a type that can be
plugged directly into a prepared "slot" in the circuit board
"card-cage" that holds the circuit boards constituting the desktop
computer's other circuits. In that way the communications unit may
be tied directly into the computer's backplane wiring and receive
its electric power directly from the computer's power supply and be
wired directly to the computer's internal control busses, if such
should be found desirable.
By being closely integrated with a desktop computer, the
communications unit may be arranged to use the computer's already
existing keyboard and display screen (CRT) so that the expense of
providing these items separately for the communications system can
be spared. As an example, if the communications unit is connected
to a keytelephone system, the status of the lines, such as free,
busy, holding or ringing may be shown on the CRT screen in a
readily recognizable display, and the control of these lines,
instead of requiring separate control keys, can be undertaken by
means of the computer's already existing keyboard.
The communications unit according to the instant invention further
consists of switching elements--in this disclosure designated
"crosspoints"--for providing a flexible, selective association
between the voice and data lines, a voice telephone, the computer
and the line protocol control circuit. These crosspoints are
directly controllable by the computer and therefore also comprise
holding latch circuits that can be set or reset by the input-output
bus (I/O Bus) of the computer.
The communications unit may further comprise internal controls
consisting of a small microprocessor with associated control memory
containing a control program for the functions dedicated to the
communications unit and memory associated therewith for storing
frequently used numbers, connection patterns and protocols desired
by the user.
The communications unit may further comprise a so-called modem
(modulator-demodulator) which is a conventional circuit adapted for
data interfacing between a computer and voice and data lines. Such
modems are commercially available in different forms, but all serve
to convert computer generated data strings into a data format that
can be directly transmitted over data lines. In the herein
contemplated application, data modems of the type that operate on
the principle of frequency-shift (FSK) modulation have been found
to be well suited. Such FSK modems are available from different
manufacturers such as Motorola, Inc., under type number MC 14412
and others, in the form of single integrated circuits
("chips").
Other objects of this invention will appear from the following
description and appended claims, reference being had to the
accompanying drawings forming a part of this specification wherein
like reference characters designate corresponding parts in the
several views.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic block diagram of the communications unit,
showing the principal functional elements;
FIG. 2 is a perspective, diagrammatic view of a computer with the
communications unit installed in the computer case;
FIG. 3 is a partial simplified circuit diagram of the major
components constituting the invention;
FIG. 4 is a partial circuit block diagram of the modem and
telephone sections of the invention; and
FIG. 5 shows the principal control program modules.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Before explaining the disclosed embodiments of the present
invention in detail it is to be understood that the invention is
not limited in its application to the details of the particular
arrangements shown since the invention is capable of other
embodiments. Also, the terminology used herein is for the purpose
of description and not of limitation.
In FIG. 1, a number of communications lines are represented by line
1, line 2 and an intercom line having reference numbers 11 for the
lines 1 and 2 and 13 for the intercom line, respectively. The
number of lines 11 need not be two, it can be more than two, or it
may be one line, but for the contemplated use, the use of two lines
is considered typical. The lines 11 may be voice lines or voice and
data lines, or one can be a data line and the other one a voice
line. In the contemplated use a voice line meets generally the
criteria for a line having a frequency range of typically from 300
to 3500 Hz. A data line may have the same bandwidth as a voice
line, but may in addition have better controlled transmission
parameters, such as crosstalk, phase distortion, envelope delay
distortion, noise and so forth as generally required for data lines
operating at data speeds above 2400 bits per second.
The lines 11 and 13 typically consist of two conductors, normally
designated Tip and Ring, wherein the tip side is returned to ground
potential at the external switching location, and the ring side is
typically referred to -48 volt transmission battery. The switching
location may be a central office or a PABX for the lines 11, or may
be a typical keytelephone system of any one of a number of types of
systems. In the contemplated use of the invention, the switching
location is typically a keytelephone system which may be serving
also other keytelephones or work stations. When used within a
keytelephone system, each line 11, typically comprises, besides the
tip and ring conductor for voice transmission, a so-called A-lead,
which serves to place the line on hold when a momentary ground is
connected to the A-lead at the work station. Another line "LAMP" or
"L" is connected to a status ground-returned lamp for that line at
the work station. If the line status is "idle", i.e., the line is
not in use, the lamp will be dark. If the line is "engaged" in a
conversation, it will be constantly "on". If the line is ringing,
the lamp will be flashing at a rate of 60 interruptions per minute
(60 IPM), and if the line is in a "hold" condition, the lamp will
be "winking" at 60 IPM, i.e., the lamp is on longer than off
interrupted briefly at a rate of 60 IPM.
The intercom line 13 typically consists of a tip and a ring
conductor for voice transmission plus a signal line for audibly
signalling ("buzzing)" the line, or particular stations attached to
the line, plus a lamp conductor, as described above. All lines 11
and 13 may have individual ground connections or a common ground
for all lines.
The most commonly used method of data transmission on the lines 11
are by means of so-called modem data that are transmitted over a
voice band using various modulation and demodulation principles
that are well known and conventional. Modem data are typically
transmitted at data speeds up to 9600 bits per second, and
occasionally at higher speeds, but more often at lower speeds. The
type of modulation and data speed used is immaterial to the scope
of the present invention.
Returning now to FIG. 1, the three lines 11 and 13 enter the
communications unit, shown in dashed line box 10, according to the
teachings of the invention, from the left hand side, typically from
a keytelephone system, as described above. The three lines 11 and
13 intersect three vertical lines 24, 25 and 26, and at each
intersecting point an X, 14, indicates the presence of a so-called
crosspoint, which is a component that selectively can interconnect
the vertical and the horizontal line in typically a metallic
connection. In the preferred embodiment, the crosspoint will
consist of metallic make-contacts of a crosspoint to be energized
from an electronic latching circuit such as a so-called S-R
flip-flop, as shown in more detail in FIG. 3, and as described in
more detail below. Crosspoints, in other embodiments of the
invention, may be electronically constructed crosspoints combined
with a latching circuit. Such electronic crosspoints are available
as transistors FET's or SCR's from different manufacturers and have
long been known and used. Each of the vertical lines 24, 25, and 26
is connected at the bottom of FIG. 1 to a separate function block,
namely the line control 19, the modem 18 and the telephone network
17. The communications unit 10 also comprises a so-called
microcomputer 15 which in the preferred embodiment is a so-called
computer-on-a-chip. Such very small computers are available from a
number of manufacturers such as Motorola, National Semiconductor,
Zilog Corp. and others. The microcomputer contemplated in the
preferred embodiment is a so-called 6803 from Motorola which
comprises a Central Processing Unit (CPU) 25, a Read-Only Memory
(ROM) 26, a Random Access Memory (RAM) 27 and an interface circuit
(IF) 28. The above circuits are interconnected on the chip by means
of a bus 24, which is also accessible from outside the chip 15.
A Line Monitor circuit 12 operates to monitor the status at all
times of the lines 11 and 13, and "reports" the status to the
microcomputer 15. A crosspoint control circuit 16 operates to
control the setting and resetting of the individual crosspoint in
response to instructions received from the microcomputer 15.
The communications unit, according to the invention is, as stated
above, shown in the dashed line box 10. In its physical
realization, it is assembled on a single so-called printed circuit
board which is equipped with a suitable card-edge connector for
plugging into a prepared slot in a typical desktop type computer.
Such an installation is shown in the perspective view of FIG. 2,
wherein the housing 20 represents a desktop computer comprising a
backplane 33 consisting of a number of card edge receptacle
connectors 32, all mounted on a common frame 31 and wired together
with backplane wiring generally at 33. The desktop computer 20
consists of, typically, a number of printed circuit boards 34,
which contain all the various circuits required by the desktop
computer 20, such as CPU, which is separate from the CPU 25
described above under the description of the microcomputer 15, and
electronic memory circuits which store the computer's various
operating programs and store intermediate data as required. The
electronic circuit boards comprise interface circuits required to
operate various peripheral systems that are part of the computer
such as the monitor 22 with the CRT screen, the keyboard 21, and
others, not shown, which are typically disk drive, printers and
others. A power supply unit 40 also contained in the housing 20 is
connected to the main AC power 42 and supplies power to all the
circuit boards 34 via a power line 39, including the communications
unit 10 according to the present invention. The communications unit
10 also has attached thereto two multiwire cables 35 and 36 each
terminated in a plug 37 and 38, respectively. The cables 35
represents the two lines 11 of FIG. 1 and 36 represent the line 13.
The plugs 37, 38 are advantageously of the so-called modular type
now most commonly used for connection with a telephone network. The
cables 35,36 exit from the housing 20 through suitable openings in
the sides thereof. There are two other cables leaving the unit 10,
namely, the cable 23a connected to the hand set 23 and a cable 9a
connected to an audible buzzer 9, both seen on FIG. 1.
The desktop computer 20 may be any one of a number of such
computers that are now commercially available from a number of
manufacturers. Some of the best known are IBM, Hewlett-Packard,
Apple and many others. The details of the construction of the
computer 20 is immaterial to the scope of the present invention, as
long as the chosen computer has prepared slots 32 in the backplane
that are available for a so-called universal board. An IBM personal
computer has been used successfully in a practical realization of
the invention.
Referring again to FIG. 1, the individual circuit blocks
constituting the communications unit 10, mentioned briefly above,
will be described in more detail referring also to FIG. 3.
The microcomputer 15, which is a 6803-type "computer-on-a-chip"
manufactured by Motorola contains the control programs stored in
the ROM 26 which is part of the chip. The control programs are
listings of binary encoded instructions. Each one of these
instructions represent a unitary step to be performed by the
communications unit 10.
Use of stored programs for undertaking complex control functions is
now a widely used and well known art. The construction of
microcomputer systems and control programs are described in
textbooks, such as Microcomputer-Based Design by J. B. Peatman,
ISBN 0-07-049138-0, published by McGraw-Hill and Computer
Organization and Programming by C. W. Gear, ISBN 0-07-023076-5,
also published by McGraw-Hill, and others which need not be
described in detail here, since they are readily available.
The CPU 25 is capable of reading the instructions of the control
programs one at a time and executing the instructions at a very
high speed. Some of the instructions or strings of instructions
require that certain data be stored temporarily for later use. Such
temporary storage is provided by the Random Access Memory (RAM) 27.
Other instructions result in commands to be performed outside the
microcomputer 15, such as the setting and clearing of crosspoints
14 and others. Such commands are transmitted either directly from
the CPU bus 24 or an interface circuit (IF) 28. Other instructions
require that the CPU obtain information and data from other parts
of the communications unit 10, and such information is typically
transmitted via the IF circuit 28.
The control programs typically consist of smaller sections, called
modules, wherein each module serves to perform a smaller,
well-defined task within the entire program. FIG. 5 shows the
organization of the control program and its individual major
modules.
In FIG. 5, a main program module 81 maintains the main control of
the remaining program modules and schedules all operations of the
remaining modules. A line protocol module 82 contains the procedure
of operating the individual lines 11, 13. A timing module generates
all timing functions required within the control program, such as
program interrupt, the line monitor function card, the monitor and
alarm functions of module 92. The crosspoint control module 84
maintains the status of all crosspoints and their operation. The
line monitor module 85 monitors the status of the individual lines
11, 12, as monitored by the line monitor 12 of FIG. 1. The data
protocol module 86 is called in to insure the proper operation of
the modem 18. The directory module 87 controls directory
information and connection patterns as required by the user. The
line control module 88 interacts with the line control circuit 19
in response to inputs from the directory module 87, the line
protocol module 82, the timing module 83 and the crosspoint control
module 84 to control the line control circuit 19. The line control
module also interacts with input-output control module 91, which in
turn controls the interface circuit 28. A line status module 89
maintains a record of the status of lines in response to the line
monitor module 85, and in turn inputs to the input-output control
module 91. The monitor and alarm module monitors the operation of
the entire system and attempts to correct minor malfunctions. If
unable to restore operation, it sends an alarm indication to the
computer 20 for indication on the monitor 22. It should be
understood that the entire control program consisting of the
modules described in connection with FIG. 5 exists only as program
instructions stored in the memory of the microcomputer 15, and that
assistance may be provided from the control program stored in the
computer 20. It should also be understood that the partitioning of
the control program can be made by the designer of the program so
that differently structured modules are produced.
The Interface Circuit 28 is connected by means of internal data
busses 28a and 28b to the various blocks of the communications unit
10, and to the desktop computer 20, so that information and data
may be exchanged through the bussses.
The Line Control circuit 19 may be connected with either one of the
two lines 11 via the vertical line 24 and the associated
crosspoints 14. The line control unit serves to access either line
by being connected thereto through the appropriate crosspoint 14. A
line is seized by placing a resistance bridge across the tip and
ring conductor as shown in more detail in FIG. 3, wherein the line
11 is accessed by operating the crosspoint relay LA, 49, which in
turn closes the crosspoint make contacts 46, 47 and 48. With make
contacts 46 and 47 closed, a DC-connection may be established
through the make contacts 58 of the relay PLS through the two
balanced primary windings a and b of the transformer 57. When the
line is seized, DC-current, supplied from the switching center,
flows through the above described connection, and dial tone is
supplied from the switching center. A connection may be established
to a remote terminal by dialling the number of that terminal. The
dialling is performed by pulses in the form of short current
interruptions produced by the make contacts 58 of the relay PLS.
The relay PLS is in turn controlled by the flip-flop 59 which is
set and reset via set and reset leads connected to the interface
circuit IF via the internal bus 28b (FIG. 1) and finally under
control of the CPU 25 and the control program stored in the ROM 26.
Control of the switching operation may alternatively be performed
by means of the sending of dual-tones produced by the DTMF tone
sender 61 in a manner analogous to the use of a conventional push
button telephone. After a connection has been successfully
established by the line control circuit 19, in the normal course of
events, the line connection will be "handed over" to one of the
other circuits, such as the modem 18, if an exchange of data is to
be performed with another computer or to the telephone network
circuit 17, if a speech connection is to be established. In the
course of establishing the required connection by the line control
circuit 19, various conditions such as normal busy tone, in the
form of 60 IPM may be encountered, or a path--busy tone, 120 IPM,
may be received, indicating that a temporary network congestion
condition is encountered. Such tones may be received by the tone
receiver 62 connected to the line 11 via the winding d of the
transformer 57. The tone receiver 62 converts busy tones and other
call progress tones to logic-level DC-signals that are transmitted
via the bus 28b to the micro-computer's IF circuit 28 for
interpretation. The micro-computer may, upon receiving such
information, make a decision to wait and send again, or dial a
different number depending upon instructions issued by the control
program.
The tone receiver 62 may also have the capability of receiving DTMF
tones, which are stated above, are the special double tone
combinations selected as standard in the Western Electric Touch
Tone.RTM. system for tone signalling from push button telephones.
Call progress tones, DTMF tones and other types of tones used in
network signalling are described in books published by the AT&T
company, such as "Notes on Long Distance Dialling", issued 1975 by
AT&T. With the tone receiver 62 having DTMF tone receiving
capability, the line control 19 can receive information in DTMF
tones from a distant connected terminal and translate that
information into a format that may be received by the microcomputer
15 or in turn by the desktop computer 20. The format conversion is
advantageously performed by the interface circuit 28.
When the communications unit is operated in conjunction with a
keytelephone system, as described above, there may be a need for
placing one of the lines 11 in a hold condition. The relay HLD 60
performs this function by being momentarily operated by placing a
ground from its make contact on the vertical lead 64, which, via
the closed make contact 48 is transmitted via the A-lead to the
keytelephone system's control unit, the so-called KSU which in turn
places a holding bridge on the line 11. The hold condition, in
accordance with conventional keytelephone practice, is memorized in
a holding relay associated with the particular line 11, and allows
the line control 19, or any other instrumentality connected to the
line, to disconnect itself from the line without disturbing the
hold condition, so that the line control 19, after being
disconnected, may access another line in whichever way required
under control of the microcomputer 15.
Briefly summarizing the operation of the line control 19, that
circuit serves generally to dial up connections on any line
connected to the communications unit and to monitor that line
during the dialling up process, and to establish connection with
the distant terminal connected to the line by means of tone sending
and receiving "hand-shake" protocol used by the line and the
terminal. The line control 19 is normally intended to stay with a
line for the duration of such operations, and will normally again
disconnect from the line when that service line has been performed,
and will release the line to another user, which may be a voice
telephone or a data set.
In a simplified embodiment of the invention, the line control
functions, when they are uncomplicated, may be integrated by the
other line users, such as the modem 18 or the telephone network
17.
The crosspoint control circuit 16 consists of relays 49 and the
associated flip-flops 50, seen in detail for a single crosspoint in
FIG. 3 in the dashed line box 16. In FIG. 3, a single crosspoint
between one of the horizontal lines 11 and the vertical lines 24 is
seen consisting of three make contacts 46, 47 and 48 serving tip,
ring and A-lead, respectively, under control of the coil of the
relay LA, 49, (Line Access). The coil of LA 49 in turn is
controlled by the SR flip-flop 50, having an output lead Q driving
the relay coil, a set lead S and a reset lead R connected to the
AND-gates 51 and 52, respectively, each having three inputs, of
which the two top ones, X and Y are connected to an address decoder
53 which provides a two-lead address for any crosspoint. The bottom
input is connected to a reset and a set lead respective from the
interface circuit 28 of the microcmputer 15. In this way any
crosspoint flip-flop 50 can be selected by the microcomputer and
the control program by presenting an address to the IF 28 and a set
or reset command 56 or 55, respectively. The flip-flop 50 maintains
the relay LA 49 in its set or reset condition as required. This
procedure for setting relays, crosspoints and any other devices is
well known from computer technology and is conventional.
A line monitor circuit 12 operates to monitor the line status of
any line 11 or 13 at all times. Line status conditions are
typically line free, line ringing, line talking, line hold and
others. In the event that a line is connected with a key system,
the line status is indicated visually by the rate of the flashing
of the line lamp under control of the LAMP lead 44. In machine
communication, it is normally necessary for the machine to
determine the line status by interpreting the rate of on and off
condition of the LAMP lead 44. This interpretation is done in the
microcomputer 15, via the interface IF 28 based on an output from
an addressable AND gate 65, having two address inputs X, Y from an
address decoder connected to the IF 28, and analogous to the
address decoder 53 for the crosspoint control, and therefore not
shown. An input to the amplifier 64 is connected to the lamp lead
44 and serves to convert the voltage level on the lamp lead to a
level compatible with the AND-gate 65. In this way both or all the
lamp leads 44 are scanned in rapid succession and their flashing
rate determined, which in turn is translated into a line
status.
In the event that a line 11 is not connected with a keytelephone
system, the line status may be monitored by means of a voltage
sensing element 61a having inputs connected to the tip and ring
leads 41 and 42, and an output connected to addressable AND gate
65, which is in turn connected to the microcomputer 15 via the IF
28 for determining the line status on the basis of the voltage
between tip and ring. Typically, a 48 volt (approximately)
differential indicates an idle line status. A somewhat lower
voltage indicates busy status, and ringing is indicated by the
presence of AC-voltage of approximately 60-100 volts ac. The line
voltage sensing element may advantageously be a so-called
analog-to-digital converter which is available from several
manufacturers and which produces a binary encoded representation of
the input voltage which is directly readable by the microcomputer
15.
FIG. 4 shows two additional circuit sections of the communications
unit, namely the modem section 72 and the telephone section 71. The
modem section 72 includes the modem 18 and its crosspoint 14. The
modem section 72 includes the modem 18 and its crosspoint 14 for
connection with one of the lines 11. The crosspoint 14 consists, as
described above, of the make contacts 46,47 for connection to the
tip and ring, respectively, and the relay 49 and its associated
flip-flop 50. The modem may be any one of a number of types
available as an integrated circuit in a form that allows it to be
directly installed on the printed wiring board 10. The modem 18 is
connected directly to the desktop computer via the connection 18a
which is typically part of the computer backplane wiring 33. The
modem is also advantageously connected via the internal wiring 18b
on the circuit board 10 to the microcomputer 15. In operation the
modem 18 may communicate with the line in a number of forms. One
such form is the so-called Frequency-Shift Modulation (FSK) which
provides two-way full duplex data communication with a remote modem
via the telephone line at moderate data speeds, by means of two
frequency modulated carrier frequencies, one for each direction of
transmission.
The telephone section 71 includes a telephone network 17, that can
be connected via the vertical line 26 and the crosspoint 14, having
make contacts 46 and 47 to the tip and ring of the line 11. It may
be connected in the same manner to other lines, as seen in FIG. 1.
The telephone network 17 is an integrated telephone circuit such as
the MC 34010P from the Motorola Co. The telephone network provides
the functions required by standard telephones, best known under
various type numbers and standards established by the At&T
Company. The telephone network provides the functions required in
matching the standard handset with a standard carbon transmitter
and a standard magnetic receiver with a standard telephone line of
600-900 ohm characteristic impedance. The network also provides
so-called antisidetone suppression and protection against switching
noises and other functions. The network chip provides terminations
for a handset 23, and an off-hook switch 24 connected to the
network via lead 24a. The off-hook switch is operated by the weight
of the handset. A telephone ringer 9 is connected to the telephone
network by the lead 9a. An optional tone keysender 74 is connected
to the telephone network via leads 74a. The keysender 74 may be
deleted and its function may be performed by the DTMF tone sender
61 described hereinbefore under the description of the Line Control
19 under control of the keyboard 21. In that case, the sending of
telephone numbers is initiated from the keyboard 21 of the desktop
computer 20.
Using the desktop computer's keyboard provides the advantage that
direct access alpha-numeric keys allows the user to key-in numeric
codes that are directly translated in the desktop computer's memory
space into direct dialled telephone numbers that are transmitted
over one of the lines 11 by means of the line control circuit 19,
which is called into service for that purpose for the duration of
time required to set up the connection.
As an example, if a user of the communications unit wishes to call
a person known to him by his last name, the user merely keys into
the desktop computer's keyboard the person's last name (instead of
looking up that person's last name in a telephone directory), and
the computer, in a translation table provided for that purpose,
finds that person's number and possibly a group of numbers on which
the person may be found.
That person may further have a special private number that must be
dialled into a screening device before that person is alerted. Such
private, or "unlisted" numbers may also be found in the aforesaid
translation table. Furthermore, in order to reach the wanted
person, the user may dial through a special telephone facility for
long distance dialling or a private line network requiring special
access codes and billing numbers. All such dialling procedures may
be stored in the address translation table; so that a user of the
communications unit need only key in with a few keystrokes the
identity of the party the user wishes to reach. The process of
establishing the connection may then be undertaken by the
communications unit with the aid of the control programs stored in
the computer memories.
The use of the desktop computer's keyboard has the additional
advantage that lettered messages can be sent directly from the
alpha-numeric keyboard 21. Such a message may be sent in ASCII
(Acronym for American Standard Communications Information
Interchange) code. The message must be sent to a terminal that is
prepared to receive this code. The process of setting up such a
connection will consist of the following steps:
1. The communications units user at the keyboard 21 keys in the
desired destination code.
2. When the code is in and has been accepted by the desktop
computer 20, the line control circuit 19 is activated to set up the
connection as described above.
3. When the distant terminal is connected, it sends a confirmation
tone, which will be recognized by the modem circuit 72 which, by
this time has been connected to the same line 11.
4. When the modem receives the confirmation tone, also called
receive tone, a corresponding answer tone called transmit tone is
returned.
The two tones establish the fact that a complete connection is
present. Data representing any type of message can now be exchanged
between the two terminals, using FSK modulation on the two tone
carriers in a well known conventional manner. During the message or
data exchange, the line control circuit is released and the
connection is held by the modem at each end while the line control
circuit is free to establish other connections on other lines as
required.
* * * * *